- Interoception
- The sense of the physiological condition of the body — including signals from the cardiovascular system (heartbeat, blood pressure), respiratory system, gastrointestinal tract, musculoskeletal system, and skin. A. D. Craig proposed that a distinct afferent pathway (the lamina I spinothalamic tract → posterior insular cortex) conveys all interoceptive signals to the cortex. The anterior insula integrates these signals into a holistic bodily state representation that underlies subjective "feelings." Individual differences in interoceptive accuracy (measured by heartbeat detection tasks) predict emotional awareness, decision-making under uncertainty, and vulnerability to anxiety and depression.
- Posterior insula
- The primary interoceptive cortex, receiving ascending homeostatic signals from the body via the thalamus (particularly the ventromedial posterior nucleus, VMpo). The posterior insula is the primary somatosensory cortex for pain (specifically the affective-motivational dimension), temperature, itch, touch, and visceral sensations. It also functions as primary gustatory cortex — Penfield's stimulation studies showed that electrical stimulation of the posterior insula produced taste sensations.
- Anterior insula
- The integrative hub of the insula, where posterior interoceptive signals are combined with emotional context, salience, and cognitive signals arriving from the orbitofrontal cortex, anterior cingulate, and amygdala. The anterior insula is activated by pain (especially its unpleasantness), disgust, empathy, risk and uncertainty, craving, moral emotions, love, music, laughter, and the subjective sense of agency. Craig proposed the anterior insula as the substrate of a "global emotional moment" — the bodily grounding of consciousness.
- Disgust and the insula
- Disgust — an emotion evolved to reject contaminated food and social threats — is the most consistently insula-linked emotion. The insula and basal ganglia (particularly the putamen) reliably activate during disgust experience and during viewing images of disgusting stimuli. Patients with Huntington's disease, which damages the insula and striatum, show specific deficits in recognising disgust in facial expressions while leaving other emotion recognition largely intact (Calder et al., 2000). The connection reflects the insula's gustatory and visceral monitoring role: disgust is a visceral rejection response that the insula implements cortically.
- Empathy and the insula
- Tania Singer's landmark (2004) neuroimaging study showed that the anterior insula activates both when participants experience pain themselves and when they observe a partner in pain. This "shared representation" of pain — mediated by the anterior insula and anterior cingulate cortex — is thought to underpin empathy: we feel another's pain through the neural circuits used for our own. Individual differences in insula activation during empathy correlate with self-reported empathic concern. The insula is also activated during empathy for other emotional states (fear, disgust, physical contact).
- Insula and addiction craving
- Naqvi et al. (2007) found that smokers who sustained insula damage were dramatically more likely to quit smoking immediately and without craving or relapse compared to smokers with damage elsewhere. This implicated the insula in the interoceptive dimension of craving — the bodily "urge" that drives drug-seeking. Subsequent research has found insula involvement in craving for alcohol, cocaine, opioids, and food, establishing it as a potential therapeutic target. The insula appears to represent the bodily state associated with drug effects, which when activated by cues generates the felt urge to use.
- Salience network
- A large-scale brain network centred on the anterior insula and dorsal anterior cingulate cortex, identified through resting-state fMRI connectivity analyses. The salience network responds to emotionally, biologically, or cognitively relevant stimuli and is proposed to coordinate switching between the default mode network (self-referential, resting) and the central executive network (task-focused). Disruption of the salience network — particularly anterior insula dysfunction — has been implicated in schizophrenia, frontotemporal dementia, autism spectrum disorder, and major depression.